This invention relates to camshafts having a deactivatable cam.
Camshafts having deactivatable cams have several advantages because they allow intake and outlet valves to be opened and closed, or to be kept closed, in accordance with instantaneous operating conditions of the engine by activatinq or deactivating an associated cam. For example, when an engine has two intake valves and each intake valve is operated by a separate cam that opens the valve for a specific time, it may be practical to allow both valves to operate only at higher engine speeds in order to accommodate the load and to keep one valve closed at lower engine speeds while the other valve, which is optimally designed for lower speeds, continues to be activated by its associated cam. Another application for this type of camshaft is in an internal combustion engine having cylinders which can be rendered inactive. Since all the intake valves for a cylinder in this type of engine can be kept closed when the driver of the vehicle manually deactivates their associated cams, the engine can be operated in an economy mode at less than full load using only some of its combustion chambers.
Camshafts having at least one cam that can be deactivated are disclosed, for example, in German Offenlegungsschrift No. 39 2 938. Such conventional camshafts have sleeves which are hydraulically driven along the shaft. These sleeves are components of dog clutches provided for each cam. The cams are normally deactivated and will rotate along with the shaft only when the sleeves are in a particular axial position and the clutches are engaged.